GB1488572A - Satellite communications systems - Google Patents

Abstract

1488572 Satellite TDMA communication system SIEMENS AG 3 Jan 1975 [14 Jan 1974] 226/75 Heading H4M In a satellite communication system wherein transmitted bursts comprising TDM signal channels together with a preamble from different ground stations are combined in time staggered fashion to form a TDM block at a satellite and are retransmitted therefrom, the time required for phase correction of a burst before it is initially transmitted from a ground station is considerably reduced relative to that required in the prior art. For a particular ground station BSt2 to effect initial access it transmits an initial access signal (operation (a) (Fig. 3)) at a substantially lower level than effective signals to the satellite Sa, receives this initial access signal when retransmitted from the satellite and monitors the position of the signal as it appears in the TDM block (b). As a result of this the transmission phase at the ground station is adjusted to an intermediate phase, displaced from the desired proper phase at which burst transmission should occur by about half the possible tolerance in measuring the phase deviation between the initial access signal and the desired phase (c). The burst preamble adjusted to this intermediate phase is then transmitted (d) and is fine adjusted to the intermediate phase by a burst transmission phase control system making use of the ground stationsatellite loop (e). The burst preamble is next incrementally phase shifted by a programmed control arrangement not using the station-satellite loop to the desired phase (f). Thereafter the complete burst is transmitted (g) and held at the desired phase by the station-satellite phase control system.